This invention relates to compressed air storage (CAS) systems. More particularly, this invention relates to CAS systems that provide increased system efficiency, lower emissions and reduced system cost compared to known CAS systems.
CAS systems are well known. Such systems, often used to provide an available source of electrical power, often use compressed air stored in an air tank that is heated and routed to drive a turbine which powers an electrical generator.
Alternatively, rather than heating compressed air from the air tank prior to it being supplied to a turbine, some CAS systems utilize larger pressure tanks and forego the heating process.
One known configuration of a CAS system includes a motor that, when powered by utility power, compresses air into a tank. When electrical power is desired, compressed air from the pressure tank is routed through a fuel-combustion system that heats the compressed air before it enters the turbine inlet. This hot air drives the turbine, which in turn powers an electrical generator.
Such known CAS systems, however, suffer from various deficiencies such as wasted heat during the air compression process, which can result in higher overall operating costs, and a constant requirement for fuel to continuously heat the compressed air. In particular, the fuel-combustion process used in prior CAS systems in order to heat the compressed air produces harmful emissions, and depending on the duty cycle of the heating process, may not provide the most cost effective method of heating.
In view of the foregoing, it is an object of this invention to combine a conventional CAS system with thermally stored energy to provide a combined thermal and compressed air storage (TACAS) system that eliminates the necessity for a fuel-combustion system and the associated hydrocarbon emissions or reduces the quantity of fuel required for system operation.
It is also an object of the present invention to provide a TACAS system that reduces the amount of wasted heat during the air compression process, thereby being capable of supplying electrical power with increased efficiency over prior CAS systems.